In the existing Transmission Control Protocol (TCP) or Internet Protocol (IP) framework, the IP address of a MN represents the location of the MN. When a Corresponding Node (CN) sends a packet to the MN, the route is determined by the network in which the IP address of the MN resides. When the MN moves from its home network to a foreign network, a packet destined for the MN is still routed to the home network of the MN. In view of the fact that the MN is not within its home network, the packet will be discarded at the home network of the MN, and, accordingly, the communication between the MN and the CN is broken down.
With development of the mobile communication technology, future mobile networks must be based on IP, and the existing communication is required not to be broken down, even when the MN roams or migrates to a foreign network from its home network. The traditional TCP or IP cannot meet such requirement for the above mobile communication. Then, Internet Engineering Task Force (IETF) proposes Mobile IPv4 (MIP4) and Mobile IPv6 (MIP6).
MIP4 and MIP6 provide methods, which allow a MN to perform communication by still using its home IP address, even when roaming across IPv4 and IPv6 networks, respectively.
MIP4 provides a triangle routing mode. In the triangle routing mode, because a CN does not know whether a MN has moved, a packet destined for the MN is still sent directly to the home address of the MN. After the packet is routed to the Home Agent (HA) of the MN, it is sent by the HA to the Care-of Address (COA) of the MN through a tunnel. Data destined for the CN from the MN is directly sent to the CN.
MIP6 provides two routing mechanisms: a bi-directional tunnel mode and a route optimization mode.
In the bi-directional tunnel mode, a packet destined for a MN is still sent directly to the home address of the MN, because a CN does not know whether the MN has moved. After the packet is routed to the Home Agent (HA) of the MN, it is sent by the HA to the Care-of Address (COA) of the MN through a tunnel. Data destined for the CN from the MN is sent to the HA through a tunnel, and then is sent to the CN by the HA.
In the route optimization mode, a MN registers with a CN first, and then data sent from the MN to the CN skips the HA and is sent to the CN directly. Data sent from the CN to the MN also skips the HA and is sent to the COA of the MN directly.
The IPv4 and IPv6 networks will co-exist for a long time. Then, it is likely that a mobile node may roam across the IPv4 and IPv6 networks. Such a MN roaming across the IPv4 and IPv6 networks is referred to as a dual-stack MN. In the conventional implementations, both the HA and the MN are required to support dual-stack, to have both IPv4 and IPv6 addresses, and to support both MIPv4 and MIPv6.
In the prior art, there is a solution when a dual-stack MN roams into an IPv4 network, in which a Tunnel Broker technique is used for the dual-stack MN to roam in the IPv4 network. The MN accesses the IPv4 network through a Tunnel Broker, and routing in the IPv4 network is performed by the Tunnel Broker.
In implementation of the present invention, the inventors have found that the above solution when the dual-stack MN roams into the IPv4 network has some drawbacks as follows.
1. A lot of Tunnel Brokers have to be deployed, and the networking cost is too high, accordingly.
2. The conventional Tunnel Broker technique has to be relied on greatly, but the outlook of this technique is uncertain.
Another prior art solution for a dual-stack MN is to allow the dual-stack MN to obtain an IPv4 address in an IPv6 network.
In implementation of the present invention, the inventors have found that said another prior art solution for a dual-stack MN also has some drawbacks. That is, only a method is provided for the dual-stack MN to obtain an IPv4 address in an IPv6 network, but no method is provided for the MN to roam across the IPv4 and IPv6 networks.
Another prior art solution for interworking between IPv4 and IPv6 is to interwork between IPv4 and IPv6 in the form of Protocol Translator (PT) or tunnel.
In implementation of the present invention, the inventors have found that said other prior art solution for interworking between IPv4 and IPv6 has a drawback, in that the problem in mobile IP cannot be solved. Additionally, in the NAT or PT manner, the packet header has to be modified, which will cause many problems.